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El Pantanal: un ejemplo del impacto geomorfológico sobre el ambiente

Autores/as

  • Jean Tricart Centre de Gégraphie Appliquée, Université Louis Pasteur

Resumen

The Pantanal trough is located at the border line of the "couverture tabulaire"
at Mato Grosso Plateau, under control of faults and Precambrian metamorphic and
crystalline continental crust with Apalachian Eocambrian sedimentary landforms.
Modern alluvial formations have been formed at least 200 m below present sea
level, having around 300 m thickness. Thus, the Pantanal is a tectonic trough,
completely bordered by the 200 m contour line. Subsidence explains gentle
slopes, which are lesser than 1%. At the sheet flood fan axe. River floods are
running slowly from neighbor mountains areas, allowing a grassland support for
more than 5.000.000 of cattle.

Pantanal alluvial deposits have built enormous coalescent sheet flood fans.
The largest one is Taquari, which cross over residual mountain chains at the
right hand border of the Paraguay, covering "glacis" (bahadas) lying at its ground.
On the contact between this sheet flood fans and the "glacis" there is a
series of receptacle lakes, which are by the Paraguay floods. Some lakes
restore water to the Paraguay River during its low level after floods.

During recent Quatemary dry periods the high Paraguay basin was endorreic.
So, a number of Pantanal sheet flood fans are digged by wind erosion, forming
troughs. These troughs are partly covered by lagoons and partly by amphibious
vegetation, thus increasing runoff deficit. Therefore, the Pantanal plays an important
role on the Paraguay hidrology, emphasizing floods but increasing runoff
deficit.

It has been suggested to build large dams to regulate water flow in the rivers,
near their entrances into the Pantanal. However, this radical change in
environmental management needs a lot of knowledge, specially on this very complex
and feeble environment, where, as a consequence, investments are very expensive.